update variable initializer

Author: takev

doc/language/syntax/expression.md

@@ -7,7 +7,7 @@
 [_name_](name.md) __|__
 [_injected-variable_](injected_variable.md) __|__
 [_positional-variable_](positional_variable.md) __|__
-[_variable-declaration_](variable_declaration.md) __|__
+[_variable-initializer_](variable_initializer.md) __|__
 [_operator-expression_](operator_expression.md) __|__
 [_if-control-expression_](if_control_expression.md) __|__
 [_while-control-expression_](while_control_expression.md) __|__

doc/language/syntax/statement.md

@@ -3,6 +3,7 @@
 ## Syntax
 
 [_expression_statement_](expression_statement.md) __|__
+[_variable-declaration_](variable_declaration.md) __|__
 [_return_](return.md) __|__
 [_result_](result.md) __|__
 [_yield_](yield.md) __|__

doc/language/syntax/variable_declaration.md

@@ -2,7 +2,7 @@
 
 ## Syntax
 
-[_storage_class_](storage_class.md)__?__ [_binding_mode_](binding_mode.md) [_name_](name.md) _type_declaration_**?**
+[_storage_class_](storage_class.md)__?__ [_binding_mode_](binding_mode.md) [_name_](name.md) _type_declaration_**?** `;`
 
 ## Semantics
 Declares a variable with a [_name_](name.md) which can be used in the scope or
@@ -14,8 +14,8 @@ Variable declarations may appear in the following contexts:
  - In a code block of a control-expression
  - In a class declaration.
 
-A _variable_declaration_ is a [_expression_](expression.md) which results in a
-reference to declared variable.
+A _variable_declaration_ is a [_statement_](statement.md) as it was not assigned a value,
+there can be no result.
 
 The type and coercion-method of the variable can be set by using the
 [_coerce_](coerce.md) operator on the _variable_declaration_ or on the

doc/language/syntax/variable_initializer.md

@@ -0,0 +1,32 @@
+# variable-declaration
+
+## Syntax
+
+[_storage_class_](storage_class.md)__?__ [_binding_mode_](binding_mode.md) [_name_](name.md) _type_declaration_**?** ( `=` | `+=` ) [_expression_](expression.md)
+
+## Semantics
+Declares a variable with a [_name_](name.md) which can be used in the scope or
+child scopes where the variable is declared; and initializes it.
+
+Variable declarations may appear in the following contexts:
+ - In global scope.
+ - In a function or lambda.
+ - In a code block of a control-expression
+ - In a class declaration.
+ - In an expression.
+
+A _variable_initializer_ is a [_expression_](expression.md) which results in a
+reference to declared variable.
+
+The type and coercion-method of the variable can be set by using the
+[_coerce_](coerce.md) operator on the _variable_declaration_ or on the
+[_name_](name.md).
+
+If the type is not explicitly set, the exact type of the first assigned value is
+used as the type of the variable. The coercion-method is `:=`, which means that
+any subsequent assignment to the variable must be of exactly the same type.
+
+The assignment operator can be either:
+ - `=` which assigns a value to the newly created variable, or
+ - `+=` which assigns a value to a newly created variable or calls the `+=` operator
+        an a existing variable of the same name and type.